In conventional antennas for portable telephones, for example, monopole antennas and helical antennas are used. Among these configurations, a configuration in which antenna devices are directly contacted and connected with each other is disclosed in Japanese Laid-Open Patent Publication 261,318/1999.
In recent years, in shifting the portable telephone systems from PDC (personal digital cellular) to CDMA (code division multiple access), dual mode portable telephones have been developed, in which both the PDC and CDMA systems can be utilized. In these systems, although the electric wave frequency bands used for the transmission and reception are different from each other, in a case in which information communication is performed in a predetermined frequency band, the impedance must be matched in these frequency bands. Consequently, because the system is generally designed as a guide such that VSWR (voltage standing wave ratio) in the frequency band in use becomes at least three or less than three, it is necessary to design the system to have VSWR of three or less than three for each of the frequency bands in use. However, in antennas having conventional matching circuits, the regions in which VSWR is three or less than three have been too narrow to adjust them to use for portable information terminals having plural functions; therefore, they have been difficult to adjust.
Moreover, in the conventional antenna configuration of the portable telephones, when two or more than two frequency bands apart from each other are used, antenna devices corresponding to each frequency must be mounted; additional pins, springs, matching circuits, and antenna selecting switches, for feeding each antenna device, need to be provided.
However, regarding the portable telephones in recent years, end users tend to prefer thin-and-compact types; the increase in the packaging area due to a plurality of frequency bands being used, runs counter to the trends to reduce the thickness and size thereof; consequently, there has been a problem in that product competitiveness may be lost.
In addition, in a configuration in which a matching circuit is mounted on each of the antenna devices, coils and condensers used for the matching circuit cause losses; therefore, there has been a problem in that efficiency in the electrical-signal transmission decreases.